Compressor Surge Research Articles

The Improvement of Anti-Surge Control on Air Separation Compressor

This paper mainly describes the reasons for compressor surge and damage, and provide the traditional control method, which can not meet the growing needs, the improved control method, which according to the data using least squares curve to determine surge control regression equation and make the compressor operate safely by using the fuzzy PID control algorithm on the parameter adjustment.

Effect of Diffuser and Volute on Turbocharger Centrifugal Compressor Stability and Performance: Experimental Study

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures. Several techniques were studied to increase the compressor operating range without sacrificing the compressor efficiency. This paper presents the effect of delaying diffuser stability on the compressor performance and surge line. Two different techniques were investigated, these are grooved and pinched diffuser. Moreover, the effect on retracting volute tongue on compressor performance is also studied. Pinched diffuser shifted surge line to low flow rates, while dropping pressure through compressor. On the other hand, some interesting results were obtained when using grooved diffuser, these are pressure increase at high flow rates, and choke line shift to high flow rates. While retracting volute tongue was interesting in improving compressor efficiency, and pressure lines at high speed.

Single Versus Dual Recycle System Dynamics of High Pressure Ratio, Low Inertia Centrifugal Compressor Stations

Compression systems are designed and operated in a manner to eliminate or minimize the potential for surge, which is a dynamic instability that is very detrimental to the integrity of the compressor unit. Compressor surge can occur when compressors are subjected to rapid transients such as those occurring following an emergency shutdown (ESD) or a power failure, which in turn, requires fast reaction. To prevent this from occurring, compressor stations are designed with single or dual recycle systems with recycle valves, which are required to open upon ESD. There has been extensive debate and confusion as to whether a single recycle or a dual recycle system is required and the circumstances and the conditions under which one system or the other must be used. This paper discusses this crucial design issue in detail and highlights the parameters affecting the decision to employ either system, particularly for high pressure ratio, low inertia compressors. Parameters such as gas volume capacitance (V) in the recycle path, compressor power train inertia, compressor performance characteristics, the recycle valve coefficient (Cv), prestroke and stroke time, and check valve dynamic characteristic are crucial in determining the conditions for dynamic instabilities. A simple analytical methodology based on the perturbation theory is developed that provides a first-cut analysis to determine if a single recycle system is adequate for a given compression system. The concept of an inertia number is then introduced with a threshold value that determines which recycle system to use. Techniques to circumvent compressor surge following ESD are discussed and their respective effectiveness are highlighted including when and if a delay in the fuel cutoff will be effective. An example of a case study with actual field data of a high pressure ratio centrifugal compressor employed in a natural gas compressor station is presented to illustrate the fundamental concept of single versus dual recycle systems.

Experimental Investigations of Pressure Losses on the Performance of a Micro Gas Turbine System

Pressure losses between the compressor outlet and the turbine inlet are a major issue of overall efficiency and system stability for a solid oxide fuel cell/micro gas turbine (MGT) hybrid power plant system. The goal of this work is the detailed analysis of the effects of additional pressure losses on MGT performance in terms of steady-state and transient conditions. The experiments were performed using the micro gas turbine test rig at the German Aerospace Centre in Stuttgart using a butterfly control valve to apply additional pressure loss. This paper reports electric power and pressure characteristics at steady-state conditions as well as a new surge limit for this Turbec T100 micro gas turbine test rig. Furthermore, the effects of additional pressure loss on the compressor surge margin are quantified and a linear relation between the relative surge margin and additional pressure loss is shown. For transient variation of pressure loss at constant turbine speed, time delays are presented and an instability issue of the commercial gas turbine controller is discussed. Finally, bleed-air blow-off and reduction of the turbine outlet temperature are introduced as methods of increasing the surge margin. It is quantified that both methods have a substantial effect on the compressor surge margin. Furthermore, a comparison between both methods is given in terms of electric power output.

바이오 가스를 사용하는 가스터빈 열병합 시스템의 전부하 및 부분부하 운전특성 해석

This study analyzed the influence of firing biogas on the performance and operation of a gas turbine combined heat and power (CHP) system. A reference CHP system designed with natural gas fuel was set up and off-design simulation was made to investigate the impact of firing biogas in the system. Changes in critical operating parameters such as compressor surge margin and turbine blade temperature caused by firing biogas were examined, and a couple of operating schemes to mitigate their changes were simulated. Part load operation of the biogas-fired system was compared with that of natural-gas fired system, and it was found that as long as the two system produce the same electric power output, they exhibit nearly the same heat recovery.

Diurnal Temperature and Pressure Effects on Axial Turbomachinery Stability in Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems

A dynamic model of a 100 MW solid oxide fuel cell-gas turbine hybrid system has been developed and subjected to perturbations in diurnal ambient temperature and pressure as well as load sheds. The dynamic system responses monitored were the fuel cell electrolyte temperature, gas turbine shaft speed, turbine inlet temperature, and compressor surge. Using a control strategy that primarily focuses on holding fuel cell electrolyte temperature constant and secondarily on maintaining gas turbine shaft speed, safe operation was found to occur for expected ambient pressure variation ranges and for ambient temperature variations up to 28 K when tested nonsimultaneously. When ambient temperature and pressure were varied simultaneously, stable operation was found to occur when the two are in phase but not when the two are out of phase. The latter case leads to shaft overspeed. Compressor surge was found to be more likely when the system is subjected to a load shed initiated at minimum ambient temperature rather than at maximum ambient temperature. Fuel cell electrolyte temperature was found to be well-controlled except in the case of shaft overspeeds. Turbine inlet temperature remained in safe bounds for all cases.

Effect of a map width enhancement system on turbocharger centrifugal compressor performance and surge margin

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures. Several stabilization techniques have been studied to increase the compressor operating range without sacrificing the compressor efficiency. This paper presents an experimental study on a turbocharger compressor equipped with casing treatment (a map width enhancement (MWE) system). A KKK turbocharger was modified and tested at Ecole Centrale de Nantes. The experimental programme mainly dealt with traditional compressor performance measurements for an MWE. Whereas much work has been previously carried out to study the apparatus communicating between the annular flow passage and the impeller wheel, an apparatus with multiple holes has not been previously considered. In this paper experiments have been inducted to study the effect of an MWE structure with plurality of holes on the performance and stable functioning of a turbocharger centrifugal compressor. The effect of extending the length of the inner tubular wall has also been investigated. Two different MWE configurations have been tested and results were analysed while conducting a series of tests. The experimental studies have shown that while the MWE was advantageous in increasing pressure ratio at high compressor speeds, it failed in extending the compressor map. Moreover, extending the inner tube length was efficient in significantly shifting the surge line to low flowrates, by producing a uniform flow at inducer inlet.

Potential of Using a Nozzle at the Compressor Inlet of a High-Speed Direct-Injection Diesel Engine

The present work reports the effect of a nozzle placed upstream of the compressor of a high-speed direct-injection diesel engine. It has been observed that mounting a nozzle at the compressor inlet can lead to a shift in the compressor surge line to lower mass flowrates. In order to study the effect of the nozzle on the engine performance a set of experimental investigations has been conducted including characterization of the nozzle alone using a flow test rig up to sonic conditions and characterization of the nozzle—compressor unit by determining its operation map in a turbocharger test bench. The distortions in the compressor inlet are usually considered as a disadvantage, as they affect the efficiency and the behaviour of the turbocharger. However, the comparison between the original compressor map (provided by the manufacturer) and the nozzle—compressor map given in the present paper shows that the change in the flow pattern caused by the nozzle improves the engine—turbocharger coupling and thus reduces the air mass flowrate, leading to a surge by 30 per cent, for a given pressure ratio. The improvement in turbocharging does not necessarily increase the performance of the engine. Nevertheless, the possibility of increasing the boost pressure allows elevated fuel flowrates to be applied while still maintaining the combustion efficiency, thus increasing the power of the engine

Operation window and part-load performance study of a syngas fired gas turbine

Integrated coal gasification combined cycle (IGCC) provides a great opportunity for clean utilization of coal while maintaining the advantage of high energy efficiency brought by gas turbines. A challenging problem arising from the integration of an existing gas turbine to an IGCC system is the performance change of the gas turbine due to the shift of fuel from natural gas to synthesis gas, or syngas, mainly consisting of carbon monoxide and hydrogen. Besides the change of base-load performance, which has been extensively studied, the change of part-load performance is also of great significance for the operation of a gas turbine and an IGCC plant.In this paper, a detailed mathematical model of a syngas fired gas turbine is developed to study its part-load performance. A baseline is firstly established using the part-load performance of a natural gas fired gas turbine, then the part-load performance of the gas turbine running with different compositions of syngas is investigated and compared with the baseline. Particularly, the impacts of the variable inlet guide vane, the degree of fuel dilution, and the degree of air bleed are investigated. Results indicate that insufficient cooling of turbine blades and a reduced compressor surge margin are the major factors that constrain the part-load performance of a syngas fired gas turbine. Results also show that air bleed from the compressor can greatly improve the working condition of a syngas fired gas turbine, especially for those fired with low lower heating value syngas. The regulating strategy of a syngas fired gas turbine should also be adjusted in accordance to the changes of part-load performance, and a reduced scope of constant TAT (turbine exhaust temperature) control mode is required.

Design and Characterization of a Centrifugal Compressor Surge Test Rig

A detailed description of a new centrifugal compressor surge test rig is presented. The objective of the design and development of the rig is to study the surge phenomenon in centrifugal compression systems and to investigate a novel method of surge control by active magnetic bearing servo actuation of the impeller axial tip clearance. In this paper, we focus on the design, initial setup, and testing of the rig. The latter two include the commissioning of the rig and the experimental characterization of the compressor performance. The behavior of the compressor during surge is analyzed by driving the experimental setup into surge. Two fundamental frequencies, 21 Hz and 7 Hz, connected to the surge oscillation in the test rig are identified, and the observed instability is categorized according to the intensity of pressure fluctuations. Based on the test results, the excited pressure waves are clearly the result of surge and not stall. Also, they exhibit the characteristics of mild and classic surge instead of deep surge. Finally, the change in the compressor performance due to variation in the impeller tip clearance is experimentally examined, and the results support the potential of the tip clearance modulation for the control of compressor surge. This is the first such demonstration of the feasibility of surge control of a compressor using active magnetic bearings.

1214 遠心圧縮機サージ特性に関する研究(GS-5 翼周り流れ)

1214 遠心圧縮機サージ特性に関する研究(GS-5 翼周り流れ)

Gas Turbine Engine Control Design Using Fuzzy Logic and Neural Networks

This paper presents a successful approach in designing a Fuzzy Logic Controller (FLC) for a specific Jet Engine. At first, a suitable mathematical model for the jet engine is presented by the aid of SIMULINK. Then by applying different reasonable fuel flow functions via the engine model, some important engine-transient operation parameters (such as thrust, compressor surge margin, turbine inlet temperature, etc.) are obtained. These parameters provide a precious database, which train a neural network. At the second step, by designing and training a feedforward multilayer perceptron neural network according to this available database; a number of different reasonable fuel flow functions for various engine acceleration operations are determined. These functions are used to define the desired fuzzy fuel functions. Indeed, the neural networks are used as an effective method to define the optimum fuzzy fuel functions. At the next step, we propose a FLC by using the engine simulation model and the neural network results. The proposed control scheme is proved by computer simulation using the designed engine model. The simulation results of engine model with FLC illustrate that the proposed controller achieves the desired performance and stability.

Preliminary results of active centrifugal compressor surge control using variable inducer shroud bleed

The goal of this paper is to give a short introduction to the reader into the preliminary results of the practical investigations of active centrifugal compressor surge control using variable inducer shroud bleed (VISB). After establishing the mathematical model of the VISB researches are being carried out on a compressor. There is a detailed description of the measurement equipment which covers a test bench and a data acquisition system. With the measurement and evaluation of the thermodynamic operational parameters of the compressor system, the theoretical investigation can be validated, which is also presented hereby.

Tuning of fuzzy fuel controller for aero-engine thrust regulation and safety considerations using genetic algorithm

Previous studies have demonstrated that fuzzy logic control (FLC) could be applied to the design of the gas turbine aero-engine (GTE) fuel control system. However, due to the complex nature of the gas turbine aero-engine, FLC design based on the engineering intuition frequently fail to achieve satisfactory overall system efficiency and therefore an intelligent approach based on an optimization algorithm must be used. In this paper, a genetic-fuzzy control is employed in order to meet the engine performance requirement (thrust regulation) and constraints (safety considerations). In this approach, an initial FLC is firstly designed for the engine fuel system. Subsequently, the optimal tuning of the FLC parameters is performed based on the formulation of an optimization problem solved by a multi-objective genetic algorithm (GA). For this purpose, the objective functions are set to increase the GTE dynamic performance while obtaining the desired thrust and satisfying the safety constraints. A computer simulation program is also developed to investigate the effectiveness of the approach for a single spool jet engine. The simulation results are validated by the experimental data to support the simulation model. The results obtained from the simulation show the ability of the approach to achieve an acceptable thrust performance as well as the engine protection against the safety considerations such as engine over-speed, turbine over-temperature and the surge in compressor with sufficient safe margin.

Model Validation for an Active Magnetic Bearing Based Compressor Surge Control Test Rig

In this paper, we present experimental test data for the validation of a recently introduced mathematical model for centrifugal compression systems with variable impeller axial clearances. Employing the active magnetic bearings (AMBs) of a compressor built for the experimental study of surge, the axial clearance between the impeller and the static shroud is servo controlled, and the measured variations in the compressor output flow are compared with the mathematical model. The steady state and the dynamic responses of the compression system induced by varying the impeller tip clearance are measured and compared with the theoretical predictions, and the states of the compression system in surge condition are collected and analyzed. Parameters in the compression system model, such as the Greitzer parameter B and Helmholtz frequency ωH are experimentally identified. Also, the servo dynamics of the magnetic bearing that controls the axial impeller position is determined experimentally. To further validate the mathematical model and the feasibility of using the impeller tip clearance for controlling surge, we present a design example for an active surge controller based on the derived model, and simulate the response of the compression system. This design exercise also helps us understand the possible challenges that one could face in the design and implementation of a successful surge controller.

Experimental Evaluation of the Transient Behavior of a Compressor Station During Emergency Shutdowns

The transient behavior of compressor stations, particularly under rapidly changing conditions, is of vital interest to operators. Predicting transient behavior is an important factor in avoiding damage during events such as emergency shutdowns. A limited number of “accidental” data sets from compressor manufacturers and users are available in the public literature domain. A variety of simulations and modeling approaches have been presented over the last few years at industry conferences. The available experimental data is not of sufficient quality and resolution to properly compare predictions with analytical results or simulations available in current software packages. Necessary information about the compressor, driver, valves, and geometry of the system is often missing. Currently utilized software has not been adequately validated with full-scale realistic benchmark data, as this data is not available in the public domain. Modeling procedures and results of surge control system simulations seldom contain validation data achieved through actual testing. This type of transient test data for a dynamic surge condition is often difficult to obtain. The primary objective of this work is to develop experimental transient compressor surge data on a full-scale test facility, which would facilitate the verification and comparison of existing and future transient surge models. Results of the testing and model comparisons will be documented. Relevant, dimensionless parameters will be presented and validated utilizing the test data. Conclusions from the testing and recommendations for the transient analysis software will be provided.

Robust Fuzzy Fault Detection and Isolation Approach Applied to Surge in Centrifugal Compressor Modeling and Control

This work presents the results of applying an advanced fault detection and isolation technique to centrifugal compressor; this advanced technique uses physics models of the centrifugal compressor with a fuzzy modeling and control solution method. The fuzzy fault detection and isolation has become an issue of primary importance in modern process engineering automation as it provides the prerequisites for the task of fault detection. In this work, we present an application of this approach in fault detection and isolation of surge in compression system. The ability to detect the surge is essential to improve reliability and security of the gas compressor plants. We describe and illustrate an alternative implementation to the compression systems supervision task using the basic principles of fuzzy fault detection and isolation associated with fuzzy modeling approach. In this supervision task, the residual generation is obtained from the real input-output data process and the residual evaluation is based on fuzzy logic method. The results of this application are very encouraging with relatively low levels of false alarms and obtaining a good limitation of surge in natural gas pipeline compressors.

Compressor surge control using a variable area throttle and fuzzy logic control

In this paper we present a new fuzzy control approach to compressor surge control. A variable area throttle is used in this strategy. The controller uses measurements of the mass flow rate and the change of mass flow rate to determine the control action. By using the change of mass flow rate, the controller does not need to know where the operating point is. One advantage of the proposed controller is that it does not need a mathematical model of the controlled compressor and it works on any centrifugal compressors. The fuzzy rules are transferable and only the scaling factor and the throttle capacity need to be changed when the controller is applied to another compressor of the same type. Simulation results show that the proposed controller gives good performance in various situations.

가스화 복합화력발전 플랜트에서 CO2제거가 성능에 미치는 영향 해석

In the power generation industry, various efforts are needed to cope with tightening regulation on carbon dioxide emission. Integrated gasification combined cycle (IGCC) is a relatively environmentally friendly power generation method using coal. Moreover, pre-combustion capture is possible in the IGCC system. Therefore, much effort is being made to develop advanced IGCC systems. However, removal of prior to the gas turbine may affect the system performance and operation because the fuel flow, which is supplied to the gas turbine, is reduced in comparison with normal IGCC plants. This study predicts, through a parametric analysis, system performances of both an IGCC plant using normal syngas and a plant with capture. Performance characteristics are compared and influence of capture is discussed. By removing from the syngas, the heating value of the fuel increases, and thus the required fuel flow to the gas turbine is reduced. The resulting reduction in turbine flow lowers the compressor pressure ratio, which alleviates the compressor surge problem. The performance of the bottoming cycle is not influenced much.

Modelling and Quasilinear Control of Compressor Surge and Rotating Stall Vibrations

An unsteady nonlinear and extended version of the Moore‐Greitzer model is developed to facilitate the synthesis of a quasilinear stall vibration controller. The controller is synthesised in two steps. The first step defines the equilibrium point and ensures that the desired equilibrium point is stable. In the second step, the margin of stability at the equilibrium point is tuned or increased by an appropriate feedback of change in the mass flow rate about the steady mass flow rate at the compressor exit. The relatively simple and systematic non‐linear modelling and linear controller synthesis approach adopted in this paper clearly highlights the main features on the controller that is capable of inhibiting compressor surge and rotating stall vibrations. Moreover, the method can be adopted for any axial compressor provided its steady‐state compressor and throttle maps are known.